Electrical apparatus



L. H. BURNHAM ELECTRICAL APPARATUS Filed March 25, 1922 Loc Inventor: ke 'HBur-nham;

His Atfiorney Patented Oct. 12, 1926.

,UNITED STATES v I 1, 03,063 PATENT OFFICE.

LOCKE H. BURNHAM, OF PITTSFIELD, MASSACHUSETTS, ASSIGNOR TO GENERAL ELEC- TRIO COMPANY, A CORPORATIONQQF NEW YORK.

ELECTRICAL APPARATUS.

Application filed March 23, 1922. Serial No. 546,120.

My invention relates to electrical apparatus which is cooled by being immersed. in a body of suitable liquid such as oil. The general object of the invention is to provide an improvedarrangement to care for expansion and contraction of the liquid under various conditions which may arise duringthe operation. of the immersed apparatus.

It is customary to enclose electrical induction apparatus, such as a transformer, 1!. a casing which is connected with an expan' sion chamber, the casing and exp'ansioi chamber being filled with cooling liquid tr 1a a level'above the opening of the conncctiol.

into the expansion chamber. This liquid may expand and contract slowly under the influence of var ing temperatures to which it is subjected uring normal operation of the apparatus and it may occasionally expand suddenly by reason, for instance, of the sudden generation of considerable volumes of gas resulting from accidental short circuits or arcs in the apparatus. It is desir- 26 able that the normally slow and gradual expansion and contraction of the liquid be cared for by permitting a correspondingly slow exchange of liquid back and forth between the casing and the expansion chamber,

30 the rate of exchange being sufficiently re- I tarded or restricted to prevent heated liquid being carried by convection currents from the casing to the expansion chamber. This minimizes contamination of the liquid as it is more easily oxidized by air in the expansion chamber when heated than when cool. In the event, however, of sudden expansion of the liquid, within the casing, it

is desirable that quick relief be provided in order to avoid the oceurence of excessive and dangerous pressures within the casing.

It is an object of this invention to provide a construction wherein these various desirable results may be attained. Other objects 4.5 and advantages will appear.

One embodiment of' the invention is illus- ,trated in the accompanying drawing'which shows a transformer casing connected with an expansion chamber or conservator in accordance with the principles which have been outlined. v

In this particular embodiment of the in vention, a transformer casing 1 is connected, preferably from its upper portion, by a large pipe 2 with an expansion chamber orconservator 3. -A valve 4 normally closes the opening or passageway through the pipe upper end of the pipe 2, this level being indieated by the broken lines 6. As the liquid .in the casing 1 expands and contracts under the influence of varying temperature, it is permitted to flow to and from the expansion chambcrfi-through the opening 5 which, however, is small enough to prevent convection currents. The liquid in contactwith the air in the expansion chamber, therefore, remains cool at all times so that it is substantially free from the effects of oxidation. A breather 7 permits air to pass into and out of the expansion chamber 3 as the level 6 of the liquid falls and rises. The pipe 2 preferably extendsa little above the bottom of the expansion chamber 3 so that any moisture that may settle in the liquid in this chamber cannot run down into the casing ,1 but will collect in a trap 8 whence it may be drawn off at intervals.

Upon the occurrence of an accidental fault such as a short circuit or are in the transformer, a large volume of gas may be suddenly generated and create pressure Within the casing 1. The pressure is instantly relieved and prevented from rising to excessive and dangerous values, however, by the large pipe 2, liquid and gas passing quickly into the expansion chamber 3 through this large pipe and past the valve 5 which yields to the increased pressure of the liquid and is thereby readily opened toward the expansion chamber. The resulting pressure in the expansion chamber is limited to safe values by rupture of a relief diaphragm 9 which normally closes a large outlet 10 from the expansion chamber. I A construction involving the features disclosed by this invention provides ready relief for pressures occurring in the casing of electrical apparatus immersed in a cooling liquid and danger from excessive pressures is eliminated. At the same time, the apparatus is permitted to function under nor- ,110

mal conditions ofioperation'in such manner that the liquid mayexpand and contract under the influence of varying temperature by Letters Patent of-the United States, is

1. The combination with a casing for electrical apparatus, of an expansion chamber provided with, an outlet, there being a passageway connecting said casing and expansion chamber, cooling liquid within the casing and extending through said passageway intothe expansion chamber, means responsive to pressure within the casing for varying the effective size of said passageway, and means normally closing said outlet from the expansion chamber and responsive to pressure within said chamber'to open said outlet. I 4

2. The combination with a casing for electrical apparatus, of an expansion chamber,

there being a passageway connecting said casing and expansion chamber, cooling liquid within the casing and extending through said passageway into the expansion chamber, and a valve'for limiting thermal circulation vof liquid through said passageway said valve being arranged to be opened by sudden pressure within the casing. and having an opening therethrough smaller than the passageway between the casing and expansion chamber, whereby said smaller opening permits interchange of cooling liquid between said casing and said expansion chamber due to expansion and contraction of the liquid within the casing.

3. The combination with a casing for electrical apparatus, of an expansion chamber, there being a passageway connecting said casing and expansion chamber, cooling liquid within the casing and extending casing and said expansion chamber due to through said passageway into the expansion expansion and contraction of the liquid within the casing.

In witness whereof. I have hereunto set my hand this 20th day 0T March, 1922.

LOCKE H. BURNHAM. 

